Self-locking fastener



March 24, 1970 K. NEGORO 3,502,129

SELF-LOCKING FASTENER Filed March 28, 1968 26 Free Z4 22 United States Patent O 3,502,129 SELF-LOCKING FASTENER Kaiji Negoro, Montebello, Calif., assignor to Klmatlc, Inc., Tustin, Calif., a corporation of Delaware Filed Mar. 28, 1968, Ser. No. 716,876 Int. Cl. F16b 39/16, 39/26, 27/00 US. Cl. 151-14 4 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION The fastener of the invention has particular utility in protecting removable fixtures in public places. For example, one embodiment of the invention will be described in conjunction with a Wire cage which, in turn, serves to protect light bulbs from unauthorized removal. The utilization of the fastener of the invention permits the cage to be attached to a wide range of sizes of commercial light sockets, and it is effective to prevent the unauthorized removal of the cage, and of the light bulb enclosed therein from the socket.

It will become evident as the description proceeds, however, that the improved fastener of the invention has general utility for protecting a wide range of objects, such as vending machines, plumbing fixtures, and so on, from unauthorized removal. In each instance, it is merely necessary to provide a fastener embodying the concepts of the invention, to permit the fixture to be easily and quickly mounted in place, and yet to cause the fixture to be supported in a manner so as to prevent its unauthorized removal.

SUMMARY OF THE INVENTION The self-locking fastener of the invention comprises a helical coil of a resilient material, such as steel wire. The coil is wound in a direction such that as a screw is threaded into one end of the coil, the coil tends to loosen and receive the screw. However, any attempt to unscrew the screw from the coil causes the coil to tighten around the surface of the screw so as to prevent its removal.

BRIEF DESCRIPTION OF THE DRAWINGS FIGURE 1 is a perspective view of an electric lamp and socket, and a protective cage, the cage being afiixed to the socket by means of a fastener incorporating the concepts of the invention;

FIGURE 2 is a fragmentary view of the fastener of FIGURE 1, on an enlarged scale;

FIGURE 3 is a perspective view of a fastener representing a second embodiment of the invention;

FIGURE 4 illustrates a modification of the embodiment of FIGURE 3; and

FIGURES 5 and 6 are plan and side views respectively of yet another embodiment of the invention.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS A particular type of lamp socket 10 is illustrated in FIGURE 1, this socket being designed as a receptacle for outdoor floodlights of the small projection type. These lights are used, for example, to light the exterior walls r. CO

of houses, motels, apartments, gas stations and the like. The particular flood lamp supported in the socket 10 is designated 12. The lamp 12 may be an outdoor flood lamp of the type designed PAR 38. It is to be understood, of course, that the particular lamp and socket shown in FIGURE 1 forms no part of the present invention. The invention is concerned with a self-locking fastener which, as explained above, finds utility in conjunction with a wide range of electric fixtures, or other fixtures, in order to prevent their removal.

In the particular embodiment of FIGURE 1, a cage 14 is provided which is intended to surround the lamp 12, so as to prevent its removal. The cage itself may have a hinged top 16 which may be opened to remove the lamp 12 for replacement purposes. The top 16 may be held closed on the top of the cage 14 by an appropriate lock arrangement 18. The lock arrangement 18, for example, may be a particular type of screw, which can be removed only with a special type of wrench.

In order to adapt the cage 14 to a wide variety of socket sizes, it is held on the socket by a fastener embodying the concepts of the present invention. In the particular embodiment, the cage itself may be composed of resilient steel wire. One side wire of the cage may then be deformed into a helical coil 20 as shown in FIGURES 1 and 2. The helical coil 20 has an anchoring means 20a which, in the illustrated embodiment, constitutes an extension of the right-hand end-turn of the coil, which extension is integral with the corresponding side wire of the cage 14. The anchoring means 20a supports the helical coil 20 at its right-hand end, and the left-hand end of the coil is free to move.

A second side wire of the cage 14 is configured into a loop 22 which is disposed in axial alignment with the coil 20. The cage is held on the socket 10 by means of a screw 24. The screw 24 may be a case-hardened type of screw of the self-tapping type. The diameter of the loop 22 is such that the screw 24 may be freely inserted through it, with the loop engaging the head of the screw.

The coil 20 is wound in a direction such that when the screw 24 is inserted through the loop 22 and threaded into the right hand end of the coil 20, the anchoring means 20a causes the turns of the coil to loosen radially, so that the screw may be freely threaded into the coil. However, when it is attempted to remove the screw 24 from the coil, the anchoring means 20a causes the turns of the coil to tighten down against the surface of the screw so as to prevent its removal.

That is, the coil 20 may be analogized to a spring clutch which is forced open when the screw 24 is inserted into it, yet which produces a tightening clutching action when an attempt is made to remove the screw. The coil 20 may be used as a nonclutching fastener by anchoring the free left-hand end of the coil. Then, when an attempt is made to remove the screw 24, the ability of the coil to tighten radially down on the surface of the screw is nullified.

The embodiment of FIGURE 3 is generally similar to the embodiment of FIGURES 1 and 2, and the helical coil fastener has also been designated 20 in the latter embodiment. However, the extension of the end turn, designated 20b in FIGURE 3, and which serves to anchor the coil on the member to be fastened, is formed into a loop, so that it may be attached to the said member by a machine screw, rivet or the like, instead of being integral therewith, as was the case in the embodiment of FIG- URES 1 and 2.

Likewise, the embodiment of FIGURE 4 is generally similar to the embodiment of FIGURE 3, and the helical coil again has been designated 20 in FIGURE 4, and the anchoring means has again been designated 20b.

3 However, in the embodiment of FIGURE 4, the other end of the coil, designated 200 extends radially. This provides a portion of the coil which may be torqued in an unscrewing direction to declutch the screw 24 for removal, when the screw is inserted into the coil 20. The torque application may be made with a tool, such as a short piece of tubing (as shown), pliers, or other suitable tool. The aforesaid tool is inserted over theend 20c, and turned in a direction to loosen the coil, so as to permit the removal of the screw.

In the embodiments of FIGURES 5 and 6, the pitch of the helix formed by the coil, designated 20 is variable, with the coil exhibiting a varying pitch towards the end which receives the screw. The anchoring means in the latter embodiment comprises an extension 20a of the end turned at the end which receives the screw, the end of the anchoring means 20a being turned up so as to engage the member to be fastened thereby and induce the desired locking action on the fastener.

As shown in FIGURE 5, for example, the wire nut formed by the coil 21' is used to hold a sign, or other plate 30, for example, on a post 32, by means of a screw 34', the screw and coil passing through a hole in the post. I

The various turns in the coil of FIGURES 5 and 6 are designated 0-4 respectively. The coil 20 is formed so that the turns 3 and 4 are in coaxial alignment with the axis of the screw 34, and these two turns are of reduced diameter to pass freely through the hole in the post 32. The turn 2 is then threaded through the hole to assume its position shown in FIGURE 5. The extension 20a of the end turn 0 extends up into engagement with the plate to serve as an anchoring means for the assembly, as noted above.

The turn 1, as shown in FIGURE 5 cuts across the helix formed by the coil 20' to engage the side of the screw 34.

The screw 34 may be threaded into the wire nut formed by the coil 20', after the coil has been inserted in the hole in the support member 32. When the screw is tightened down into the wire nut, turns 3 and 4 are in axial alignment with the screw, and the screw threads down into these turns, and the screw is also engaged by a portion of the turn 1. Any attempt to loosen the screw causes these turns to tighten around it to prevent such a removal.

It will be appreciated that while particular em'bodi ments of the invention have been shown and described, modifications may be made. It is intended to cover all the modifications which come within the scope of the invention.

What is claimed is:

1. A self-locking Wire nut for use with a threaded screw to secure together first and second elements, said screw extending through an aperture formed in one of said elements, and sand wire nut comprlslng a coil of resihent wire having a free end remote from said first and second elements, and further having an extension of the end turn at the opposite end thereof engaging one of said elements to form an anchoring means for said wire nut, the turns of said coil extending in a direction opposite to the direction of the convolutions of the threads formed in said screw so that when said screw is turned to be threaded into said not said anchoring vmeans causes the turns of said coil to loosen with respect to said screw to permit said screw to be threaded freely into said coil from the anchored end thereof to the free end thereof, and so that when said screw is turned in the opposite direction the free end of said coil tightens radially with respect to said screw to restrain the unthreading of said screw out of said coil, said coil having a plurality of turns in coaxial alignment withthe axis of said screw and engaging the peripheral surface of said screw when said screw is in place, and in which said coil has a further turn having a diameter normally greater than the outer diameter of said screw but deformed to extend radially across the coil to engage said screw tangentially when said screw is in place.

2. The wire nut defined in claim 1 in which the radius of successive turns of said coil decreases towards the free end thereof.

3. The self-locking wire nut defined in claim 1, in which said nut supports said first element on said second element with said nut being threaded through a hole in said second element and with said screw extending through said first element, with said anchoring means extending radially between said first element and said second element and engaging said first element.

4. The wire nut defined in claim 3 and which includes a first plurality of turns of said coil in coaxial alignment with said screw when said screw is in place and engaging the peripheral surface of said screw, said first plurality of turns extending from said free end of said coil towards the opposite end of said coil, and said first plurality of turns having an outer diameter to pass freely through said hole, and said coil including a further plurality of turns between said first plurality and the opposite end thereof of a diameter greater than said hole to be threaded therethrough.

References Cited UNITED STATES PATENTS 900,5 89 10/ 1908 Ratcliffe. 1,502,555 7/1924 Eklund. 1,630,958 5/1927 Mauch. 1,898,907 2/ 1933 Smith. 1,910,160 5/1933 Gorman. 3,165,136 1/1965 Horton 151-4l.75

EDWARD C. ALLEN, Primary Examiner US. Cl. X.R. 

